Abstract

A surface magnon-polariton can be excited by both p- and s-polarized light if at least one of the layers is a magnetic material. We present general expressions of the tangential wave vectors of s- and p-polarized light at an interface of two media. Analysis reveals additional new regimes of surface polariton resonances with magnetic materials for s- and p-polarized light. The tangential wave vectors are found to be equal in magnitude to the normal wave vectors at surface polariton resonances. The spatial distributions of the fields at resonant enhancement and the spectra of the tangential wave vectors are studied for different dielectric permittivities and magnetic permeabilities of the two media. If one of the media has dispersive dielectric function and permeability function, additional surface polariton resonance peaks appear for both s- and p polarizations. For a medium with a superconductor, the tangential component increases asymptotically at lower frequencies, providing subwavelength capability at the terahertz regime.

Figures (6)

Quadrants showing regimes of enhanced tangential wave vectors kx of surface polaritons propagating between medium 1 and medium 2 with permittivities εi and permeabilities μi for s-polarized light and p-polarized light. (a) Conventional scenario of plasmonic enhancement and its magnetic analog (indicated by open/filled dots). (b) New resonant regimes due to both electric and magnetic properties. The enhancement regions are indicated by two solid (red) lines and two dashed (green) lines slightly less and more than 1 and −1.

Tangential field distributions for s-polarized light (normalized by amplitude E0). (a) Ez field with rapid oscillations (corresponding to an enhanced tangential wave vector) and (b) Ex field with normal oscillations. Here, μ1=1 and μ2=1.008, with ε1=5 and ε2=1, corresponding to the second quadrant in the diagram in Fig. 1(b). The normalization factor is λ=2πc/ω, where ω=8×1013s−1. Note that the Ez field is continuous along y=0 but the Ex field need not be continuous (the scale is 10 times larger).

Tangential field distributions for p-polarized light. (a) Ez field with normal oscillations and (b) Ex field with rapid oscillations. Here, ε1=1 and ε2=1.009, with μ1=4 and μ2=−3, corresponding to the fourth quadrant in the diagram in Fig. 1.

Negative refractive index case: (a) real parts of ε2(ω), μ2(ω), and n2(ω)=ε2(ω)μ2(ω). Wave vector dispersions for s-polarized and p-polarized light in two situations: ε1 and μ1 with (b) the same sign and (c) opposite signs. The parameters for ε2(ω) are the same as Fig. 4. For μ2(ω), the magnetic resonance is characterized by ωμ=0.9ωε, ω~μ=1.1ω~ε, and γμ=γε.

(a) Dispersive superconductor with ε2(ω) and dispersive magnetic material with μ2(ω) (as in Fig. 5) and the resulting n2(ω)=ε2(ω)μ2(ω) with negative refractive index region. (b) The enhancement λ/λefs,p of surface polaritons for s-polarized and p-polarized light. Here, Eq. (12) is used for ε2(ω), and ω=2πc/λ and ks,p=2π/λefs,p. Other parameters are ε1=−1 and μ1=1.